The present invention relates to a control means for a horizontal boring tool according to the generic part of claim 1 and to a process for controlling such a horizontal boring tool.
In conventional underground engineering technology, laying new pipes for gas, liquids or electric lines involves considerable costs and environmental concerns. This is particularly the case when laying lines running under streets, rivers or buildings. These high costs stem from both the primary costs of the required building measures as well as from the follow-up costs of disrupting traffic or other hindrances in the respective area. Ditchless laying methods can reduce such costs and environmental concerns considerably. Therefore, various boring techniques have been employed which avoid opening surface of the earth.
The present invention relates to horizontal boring processes as, for instance, are known from H.-J. Bayer""s, xe2x80x9cPrinzipien des steuerbaren Horizontal-Spulbohrverfahrensxe2x80x9d, 3R international, Vol. 30 (1991), No. 9, pp. 511-517. In these horizontal boring processes, a cylindrical, hollow boring head, from which a rinsing fluid, for example bentonite, is pumped through nozzles, is pushed diagonally into the ground with the aid of a screwed together boring rods. Slanting of the boring head renders the boring head controllable not only regarding its feed rate respectively its thrust power but also regarding to the direction in which it moving. If the boring head is rotated evenly, it moves practically straight. If the boring head is not turned while advancing, it moves in a curved path whose direction is prescribed by the location of the incline. This design ensures the controllability of the boring head in every direction. The farther the boring head moves from the hydraulic control unit of the boring equipment, the more negatively the play and elasticity of the boring rods will influence the behavior of the system with regard to precision and stability.
In known state-of-the-art horizontal boring tools, the boring head respectively the boring lance is controlled via the advancement and the rotation of the boring rods by one person, the boring operator. The boring operator receives the information concerning the current position and location of the boring head from respective measuring sensors at the boring head. Horizontal boring tools are provided with a robust, high-resolution sensory mechanism, which continuously measures the orientation of the boring head with reference to a stationary coordinate system by measuring the roll angle, azimuth and inclination of the boring head. The respective current Cartesian position of the boring head can be determined from the current length of the boring rods in conjunction with the boring head""s preceding change in angle. In addition to the position and orientation of the boring head, the load moment of the boring rods and the pressure of an introduced boring fluid can also be detected by the sensors.
The moving behavior of the boring head is very complicated and depends strongly on the boring head""s momentary surroundings, in particular the consistency, structural constitution and the density of the earth material. Such complexity demands high boring quality and great skill on the part of the boring operator. Bore quality means here the precise as possible adherence to the prescribed boring course while avoiding collisions. The boring operator has to deduce, as necessary, correction of the rate of advancing, the rotation and the angle of rotation from the respective current orientation and position values transmitted by the sensors as well as take into account the respective momentary behavior of the boring head in the corrections. Consequently, proper operation of such a horizontal boring tool requires long training and much experience regarding the different underground behavior of the boring tool. The quality of the boring is, therefore, to a great degree dependent on the respective individual assigned as the boring operator and, furthermore, is subject to fluctuations due to tiredness. Thus, there is an increasing need for automation of the control process of a horizontal boring tool.
However, due to the great complexity of the boring procedure, it has hitherto not been possible to find suited control algorithms for a control means for such a horizontal boring tool.
The object of the present invention is to provide a control means for a horizontal boring tool as well as a process for controlling the horizontal boring tool, which automatically keeps the boring head as precisely as possible on the programmed course and reaches the target as precisely as possible independent of fluctuations in the earth consistency without any action of an experienced boring operator. Moreover, the boring procedure should require as little time as possible.
The object is solved by means of a control means according to claim 1 respectively by means of a process according to claim 10. Advantageous embodiments of the control means and of the process are the subject matter of the subclaims.
The invented control means for a horizontal boring tool is provided with an input interface for receiving the actual values of the controlled variables of the horizontal boring tool. Such controlled variables can, for example, be the roll angle, inclination and azimuth of the boring head as well as the current position of the boring head determined from these values and the rate of advancing. Furthermore, an output unit is provided which issues the control signals for steering the horizontal boring tool. Between the input interface and the output unit is a fuzzy control unit which determines the control signals by means of fuzzy logic from the actual values and the desired values for the controlled variables while taking into account heuristic process values. The heuristic process values are based, for example, on a bore operator""s long experience and comprise an engineer""s description of the movement behavior of the boring head from not exactly determined xe2x80x9cifxe2x80x94thenxe2x80x9d relationships for linking the actual values and the desired values with the corresponding control signals. In this way, know-how gathered over the years from controlling the boring heads manually can be translated into automatic control, which is especially advantageous in the present case of a control means for a horizontal boring head, because, due to the diversity of possible influences, the behavior of the boring head cannot be described physico-analytically with dynamic models.
The actual values of the controlled variables are measured by the sensors, which are provided on the boring head respectively the boring lance. Further sensors may, for example, be provided on the boring rods for determining the advancement and the angle of rotation or the rotation velocity of the rod assembly.
In the invented process, the actual values of the controlled variables of the horizontal boring tool are measured, the control signals for steering the horizontal boring tool are determined from the actual values and the desired values for the controlled variables by means of fuzzy logic while taking into account the heuristic process values, and the horizontal boring tool is steered by the control signals.
The invented control means for a horizontal boring tool and the process for controlling the horizontal boring tool permits conducting the boring procedure automatically with great aiming precision. The boring head can be made to closely adhere to a preprogrammed course independent of any fluctuations in the ground properties. The control means, therefore, permits conducting the boring procedure without employing an experienced boring operator. Fluctuations in boring speed and boring precision due to tiring are obviated. Consequently, the boring procedure can be finished faster.
The efficiency of the invented control means has already been proven in test borings.
In an advantageous embodiment of the invented control means respectively of the invented process, unlike in other fuzzy-control systems, the actual value is itself not subject to fuzzy control, but rather the variance between the actual value and the desired value.
In another advantageous embodiment, an optimizing tool based on a neuronal network (NN) is employed. In this approach, a NN learning component supplements the optimizing fuzzy control unit. This NN learning component comprises an adaptable NN model of the fuzzy control unit and a NN model of the control circuit. In a training phase preceding automatic operation, the NN control model is trained using representative training trajectories, for example using the desired trajectories until the model-actual trajectory cannot be improved regarding a selectable quality index. The optimized fuzzy parameters are now stored in the control hardware. Then automatic operation, that is automatic control and steering for the horizontal boring tool, can commence.
The control means for the horizontal boring tool is preferably realized by a digital signal processor (DSP), in which the fuzzy control unit is implemented. This DSP is preferably coupled to a PC via which the respective parameters can be entered.